Operators of Sydney's Cross City Tunnel face a backlash from motorists if they return the toll to its original $3.56, a parliamentary inquiry has warned.

Old tunnel toll 'will cause backlash'

Operators of Sydney's Cross City Tunnel face a backlash from motorists if they return the toll to its original $3.56, a parliamentary inquiry has warned.

The operators of the unpopular private tollway announced on March 5 that the one-way toll would be halved to $1.78 for at least three months.

A parliamentary inquiry into the tunnel project has recommended the standard toll not be returned to the original rate of $3.56.

"While the reduction in the toll by CCM (CrossCity Motorway Pty Ltd) is a sensible gesture, the committee believes that, if the toll is returned to its former level of $3.56 for cars at the end of the reduced toll period, there may be a backlash by motorists against using the tunnel," the inquiry's report said.

The committee recommends the government encourage the tunnel operators to lower the toll level to $2.90 once the current reduced toll period concludes.

The report also said the Roads and Traffic Authority (RTA) should ensure all toll roads advertise the cost of tolls at entrances.

The number of vehicles using future private toll road infrastructure projects should be made public on a regular basis, the report found.

The committee also recommended the government ensure motorists are advised to take precautions against air pollution in road tunnels.